The new short rod fracture toughness specimen with a circular cross section has already been used successfully for K_Ic measurements on a wide variety of materials, including brittle nonmetals. Now, a rectangular shaped “short bar” specimen which is comparable in every respect to the short rod has been developed and tested. The short bar dimensions were selected so that the geometrical constant relating K_Ic to the peak load in the experiment should be the same for both short rod and short bar configurations, according to a simplified compliance calculation. Careful comparison testing of short rod and short bar specimens of aluminum, aluminum oxide, and fused quartz have shown no experimentally significant difference in the geometrical constant. Therefore, these tests indicate that the short rod and short bar specimens can be used interchangeably, with no difference in the equation relating the peak load to K_Ic.